Push-through conditioned air vestibule and controller

ABSTRACT

A push through conditioned air vestibule unit includes an air vestibule having a top side, a first lateral side, and a second lateral side forming a passage through the unit. Movable barrier members are attached to the unit to reduce external air flow through the passage. Return air ducts are configured to circulate air to an air moving device and a temperature conditioning device. Thermal and humidity sensors measure temperature and humidity of the passage and an external room, and a system controller controls the temperature of air moved into the passage using the temperature conditioning device if the partial pressure of moisture vapor internal to the passage is not greater than or equal to the partial pressure of moisture vapor external to the passage.

CROSS REFERENCE TO RELATED APPLICATIONS

This application cross-references and claims the benefit of priority ofU.S. Provisional Patent Application No. 62/067,346, filed 22 Oct. 2014,entitled PUSH-THROUGH CONDITIONED AIR VESTIBULE AND CONTROLLER, thedisclosure of which is incorporated, in its entirety, by this reference.

TECHNICAL FIELD

The present invention relates to a conditioned air vestibule for a coldstorage doorway. More particularly, the present invention relates to anair curtain arrangement and control system that controls temperature ofthe air discharged across a doorway and a method of controlling theairflow temperature to prevent formation of frost, water, and fog.

BACKGROUND

In the field of cold storage freezers and similar devices, varioussystems such as solid doors, strip curtains, and air curtains, may beused to separate the cold storage room from an adjacent relatively warmanteroom. It is desirable to allow traffic from people and equipmentthrough a doorway between the cold storage room and the adjacent warmroom safely and with a minimum transfer of relatively cool and warm airbetween the cold room and the warm room.

The use of air curtains is one method of allowing a doorway to remainopen to traffic while also preventing substantial energy loss betweenthe cold and warm sides of the vestibule. Air curtains generally directair across the doorway to counter infiltration of warm to the cold roomand exfiltration of cold air from the cold room. By way of example, aircurtains may direct air horizontally or vertically across the doorwayfrom or toward an upper portion of the air curtain.

As a safety precaution, it is desirable to prevent the formation of fog,ice, and water in the doorway. Ice may form from the mixing of air fromthe cold and warm sides of the vestibule. The formation of ice at an aircurtain depends on the temperature and relative humidity of the cold andwarm rooms, and may be characterized by a psychrometric saturationcurve. The mixing of air from the relatively warm and cold sides may becharacterized by a straight line between points representing the warmside temperature and humidity and the cold side temperature andhumidity, which may be plotted on a psychrometric saturation chart alongwith the curve. Generally, ice may form whenever the temperature isbelow 32 degrees Fahrenheit and the mixing line is to the left of, andabove, the psychrometric saturation curve, as it is typically plotted.

The formation of ice may be prevented by heating the air discharged fromthe air curtain. By way of example, the discharged air may be heated toa temperature at a point on the psychrometric saturation chart such thatlines to such point from both the cold side and warm sidetemperature/humidity points remain to the right of, and below, thepsychrometric saturation curve, as it is typically plotted.

While avoiding the formation of ice, water, and fog, it is alsodesirable to operate the air curtain as efficiently as possible, byadding the minimum amount of heat necessary to avoid such problems. Withrespect to the psychrometric saturation chart, this means keeping thepoint representing the airstream with the added heat as close to thesaturation curve as possible, without causing mixing lines from thispoint to the cold side and warm side temperature/humidity points tocontact or cross the saturation curve.

Because temperature and humidity conditions in the cold and warm siderooms may change, it is desirable in some applications to dynamicallycondition the discharged air in response to changing conditions.Conventional systems have various shortcomings. Some systems permitoperation of the air curtain at points directly on the saturation curve.In changing environments, this permits the formation of ice, water, andfog because the system may not respond as quickly as the conditionschange and because the sensors may not be sufficiently accurate for allpositions in the vestibule. This is particularly a problem for systemsthat rely upon mathematical approximations of the psychrometricsaturation curve.

SUMMARY

An aspect of the present disclosure relates to a push throughconditioned air vestibule unit that may comprise an air vestibule havinga top side, a first lateral side, and a second lateral side that mayform a passage through the unit. A plurality of movable barrier membersmay be configured to reduce external air flow through the passage. Firstand second lateral side supply or return air ducts may be configured tosupply air to or return air from the top side from the first and secondlateral sides. An air moving device may be configured to circulate,receive, or supply air from the first and second lateral side return airducts and to move air into the passage. The unit may also have atemperature conditioning device configured to adjust the temperature ofair moved into the passage, an external thermal sensor configured tomeasure a temperature external to the passage, an internal thermalsensor configured to measure a temperature within the passage, anexternal humidity sensor configured to measure a humidity external tothe passage, and an internal humidity sensor configured to measure ahumidity internal to the passage. A system controller may be incommunication with the external and internal thermal sensors and theexternal and internal humidity sensors and may be configured to increasethe temperature of air moved into the passage using the temperatureconditioning device if the partial pressure of moisture vapor internalto the passage is not greater than or equal to the partial pressure ofmoisture vapor external to the passage.

The movable barrier members of the unit may comprise flexible stripshanging from the top side of the unit and may be impact-type doors. Adistance through the passage may be about 6 inches or greater. The firstand second lateral return air ducts may comprise return air openings atbottom ends of the first and second lateral sides.

The system controller may be configured to maintain a partial pressureof moisture in the passage equal to or higher than a partial pressure ofmoisture external to the passage, such as, for example by beingconfigured to cycle the temperature conditioning device on and off.

The air vestibule may be positioned between a first room and a secondroom, the first room having a warmer temperature than the second room.The external thermal sensor and the external humidity sensor may measuretemperature and humidity, respectively, of the first room.

In another aspect, a method of controlling air condition in aconditioned air vestibule unit is provided. The method may compriseproviding a conditioned air vestibule having a heat source, a pluralityof thermal sensors, a plurality of humidity sensors, and an air movingdevice, measuring an external temperature and a vestibule temperatureusing the plurality of thermal sensors, measuring an external humidityand a vestibule humidity using the plurality of humidity sensors,calculating an external partial pressure of moisture vapor external tothe vestibule, calculating a vestibule partial pressure of moisturevapor within the vestibule, and enabling the heat source to heat airprovided to the air moving device if the vestibule partial pressure isgreater than or equal to the external partial pressure.

The vestibule temperature and vestibule humidity may be measured withina passage through the conditioned air vestibule. The externaltemperature and external humidity may be measured from an external areawarmer than a passage through the conditioned air vestibule.

In performing the method, the heat source may be cycled on and off. Themethod may further comprise circulating air in the conditioned airvestibule unit by drawing air from a bottom of the conditioned airvestibule into the air moving device and expelling air from the airmoving device into the conditioned air vestibule after being heated bythe heat source.

Air may also be moved into the conditioned air vestibule using the airmoving device. The air moved into the vestibule may remove or preventformation of ice and/or frost in the conditioned air vestibule.

Some embodiments may comprise a non-transitory computer-readable mediumhaving instructions encoded thereon that, when executed by a processorof a computer, cause the computer to perform steps comprising: measuringan external temperature and a vestibule temperature of a conditioned airvestibule having a heat source, a plurality of thermal sensors, aplurality of humidity sensors, and an air moving device, the externaland vestibule temperatures being measured using the plurality of thermalsensors; measuring an external humidity and a vestibule humidity usingthe plurality of humidity sensors; calculating an external partialpressure of moisture vapor external to the vestibule; calculating avestibule partial pressure of moisture vapor within the vestibule; andenabling the heat source to heat air provided to the air moving deviceif the vestibule partial pressure is greater than or equal to theexternal partial pressure.

The above summary of the present invention is not intended to describeeach embodiment or every implementation of the present invention. TheFigures and the detailed description that follow more particularlyexemplify a preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings and figures illustrate a number of exemplaryembodiments and are part of the specification. Together with the presentdescription, these drawings demonstrate and explain various principlesof this disclosure. A further understanding of the nature and advantagesof the present invention may be realized by reference to the followingdrawings. In the appended figures, similar components or features mayhave the same reference label.

FIG. 1 is a perspective view of an example of a push-through conditionedair vestibule of the present disclosure.

FIG. 2 is a block diagram of modules implemented by a system controllerof a push-through conditioned air vestibule of the present disclosure.

FIG. 3 is a flowchart illustrating an example process by which a heatsource may be controlled in a push-through conditioned air vestibule.

FIG. 4 is a block diagram of a computer system that may be used toimplement embodiments of the present disclosure.

While the embodiments described herein are susceptible to variousmodifications and alternative forms, specific embodiments have beenshown by way of example in the drawings and will be described in detailherein. However, the exemplary embodiments described herein are notintended to be limited to the particular forms disclosed. Rather, theinstant disclosure covers all modifications, equivalents, andalternatives falling within the scope of the appended claims.

DETAILED DESCRIPTION

Aspects of the present disclosure may improve the effectiveness ofconditioned air vestibules such as those used to link freezers to warmerareas. These systems may reduce refrigeration load while preventingfrost, ice, and wetness at the entryway to the vestibule. An exampleembodiment of the vestibule may comprise two pairs of impact-type doors,or fixed strips, and an electrically or hot-gas heated anti-frostair-conditioning (AFC) section with temperature reset control. In somecases, the vestibule may be about 6 inches in depth in the direction oftravel through the vestibule. These benefits may reduce refrigerationlosses, increase warehouse (or other commercial or industrial location)productivity, reduce coil defrosting burdens, and improve refrigerationcycle efficiency.

FIG. 1 shows an example of a push-through conditioned air vestibule 100according to an embodiment of the present disclosure. The vestibule 100comprises a top side 102, a first lateral side 104, and a second lateralside 106 through which a passage 108 is formed. The passage 108 may belined with movable barrier members 110 on each end of the passage 108.The first lateral side 104 may comprise a first air return duct 112, andthe second lateral side 106 may comprise a second air return duct 114.These ducts 112, 114 may be configured to bring air to the top side 102from their respective lateral sides 104, 106. An air moving device 116may be positioned in the top side 102 and configured to receive air fromthe return air ducts 112, 114 and then move air into the passage 108,such as through vents exposed into the passage 108 at the top side 102of the vestibule 100. The top side 102 may also comprise a temperatureconditioning device 118 that receives airflow and adjusts thetemperature of air moved into the passage 108.

An external thermal sensor 120 may be configured to measure atemperature of external air, such as the temperature of a warm roomoutside the passage 108, and an internal thermal sensor 122 may beconfigured to measure the temperature of air in the passage 108. Anexternal humidity sensor 124 and internal humidity sensor 126 may alsobe configured to measure humidity of their respective areas relative tothe passage 108.

The vestibule 100 may also include a system controller 128 configured tocontrol the temperature conditioning device 118 and air moving device116 while receiving data from the sensors (e.g., sensors 120, 122, 124,126).

In some embodiments the vestibule 100 may comprise more than one unit,such as multiple vestibules 100 having aligned passages in a series. Thevestibule 100 may be positioned such that it separates a cooler areafrom a warmer area. A common application would be use of the vestibule100 as an air curtain between a freezer and a warm room of a warehouse,for example. In a single vestibule 100, more than one air curtain may beimplemented, such as a first air curtain directing air primarily towardthe first lateral side 104 and a second air curtain directing airprimarily toward the second lateral side 106 adjacent to the first aircurtain.

The top side 102 may include a conduit system connecting the lateralside return air ducts 112, 114 to the air moving device 116 and thetemperature conditioning device 118. Positioning the air moving device116 and temperature conditioning device 118 in the top side 102 may bebeneficial because the top side 102 is central to each of the lateralsides 104, 106, so only one air moving device 116 and/or temperatureconditioning device 118 may be required to receive and control air flowfor both lateral sides 104, 106. Additionally, positioning thesecomponents 116, 118 in the top side 102 may reduce the lateral profileof the vestibule 100, thereby either allowing the vestibule 100 to fitwithin narrower openings or to maximize the width of the passage 108.

The top side 102 in FIG. 1 is shown having the controller 128 housedtherein, but the controller 128 may alternatively be stored in anotherarea of the vestibule 100. For example, the controller 128 may bepositioned in one of the lateral sides 104, 106 to be more accessiblefrom the ground level.

The first lateral side 104 and second lateral side 106, along with thereturn air ducts 112, 114, may extend from a ground level to the topside 102 of the vestibule 100. The return air ducts 112, 114 may eachhave a return air vent 130 positioned near the ground level. At theground level, the return air vents 130 may receive cooler air that ismoved up through the return air ducts 112, 114 by the air moving device116 to the top side 102 where its temperature may be adjusted by thetemperature conditioning device 118. In an alternative embodiment, theair discharge openings may be situated near or in the floor of the aircurtain and the return vents may be situated in or near the upperportion of the air curtain, such that the air is discharged across theopening in a generally upward direction.

The passage 108 may extend between the first and second lateral sides104, 106 and may be used as a doorway between rooms on each side of thevestibule 100. In an example embodiment, the passage 108 may be about 6inches across (i.e., between the movable barrier members 110 at each endof the passage 108). The passage 108 may allow push-through access,meaning personnel, carts, vehicles, and equipment may push or movethrough the passage 108 unimpeded.

The movable barrier members 110 may comprise strips of flexiblematerial, such as, for example, vinyl strips that hang from the top side102 to the ground level. The movable barrier members 110 may beconnected by clips, fasteners, or joints to the top side 102. In someembodiments the movable barrier members 110 may be referred to asimpact-type doors. The movable barrier members 110 may provideinsulation and airflow isolation to the passage 108 by acting as abarrier to airflow while hanging vertically, yet may not hinder thepassage of equipment and personnel through the passage 108. Thus, themovable barrier members 110 may help maintain the temperature andhumidity of air within the passage 108 due to preventing the outflow orinflow of external air while they close off the ends of the passage 108.

The air moving device 116 may comprise a device that, when active,pushes or pulls air through the ducts of the vestibule 100 and throughthe passage 108. One example air moving device 116 may comprise a fan orplurality of fans that may be driven by an electric motor. The motor maybe controlled by the system controller 128 so that the speed anddirection of motion of the fan may be controlled by the controller 128.

The temperature conditioning device 118 may comprise a heating orcooling system capable of changing the temperature of air flowingthrough the ducts of the vestibule 100. For example, a temperatureconditioning device 118 may comprise a heater comprising electric coilsor heated pipes that warm the air in the ducts as it passes by the coilsor pipes. In some arrangements the temperature conditioning device 118may be controllable to output a desired amount of heat based on commandsreceived from the system controller 128. In one application, thetemperature conditioning device 118 may beneficially be a heater so thatair provided to the passage 108 may be warmer than air in a cold side ofthe vestibule 100.

The heat provided by the temperature conditioning device 118 may alsoaffect the humidity of the air in the ducts and passage 108, so in someconfigurations the vestibule 100 may further comprise a humidityconditioning device configured to increase or decrease the relativehumidity of air in the passage 108. In some embodiments, the humidityconditioning device may expel water or mist into the air at or near thetemperature conditioning device 118.

The external thermal sensor 120 and internal thermal sensor 122 maycomprise thermocouples configured to measure temperature external orinternal to the passage 108. Other types of thermal sensors may also beused. The external humidity sensor 124 and internal humidity sensor 126may comprise electronic hygrometers. The external thermal sensor 120 andexternal humidity sensor 124 may be positioned to measure temperatureand humidity of a warm room to the front or rear of the vestibule 100.The internal thermal and humidity sensors 122, 126 may measure thetemperature and humidity of air in the passage 108.

The system controller 128 may be a computing device such as, forexample, a computer or integrated control circuit. A computer systemsuitable for implementing the system controller 128 is described infurther detail in connection with FIG. 4. The system controller 128 maycomprise a plurality of modules for executing its functions. As shown inFIG. 2, a system controller 128 may comprise a vestibule control module200-a. The vestibule control module 200-a may comprise a plurality ofmodules executable by the system controller 128.

The vestibule control module 200-a may comprise a temperaturemeasurement module 205 and a humidity measurement module 210. Thetemperature measurement module 205 may be configured to receive signalsfrom the thermal sensors 120, 122 and convert the signals into signalsreadable by a partial pressure calculation module 215. Likewise, thehumidity measurement module 210 may receive signals from the humiditysensors 124, 126 and convert the signals into a form readable by thepartial pressure calculation module 215.

A partial pressure calculation module 215 may receive the signals fromthe temperature and humidity measurement modules 205, 210 and mayimplement psychrometric equations to calculate the partial pressures ofmoisture vapor in the air of the vestibule and external to thevestibule. The temperature and relative humidity of the external areaand of the vestibule may be used as inputs to these equations. In oneexample embodiment, the following equations may be implemented:

L _(o) =C ₈ /T _(o) +C ₉ +C ₁₀ T _(o) +C ₁₁ T _(o) ² +C ₁₂ T _(o) ³ +C₁₃ /nT _(o)  [Equation 1],

L _(i) =C ₈ /T _(i) +C ₉ +C ₁₀ T _(i) +C ₁₁ T _(i) ² +C ₁₂ T _(i) ³ +C₁₃ /nT _(i)  [Equation 2],

P _(wso) =e ^(Lo)  [Equation 3],

P _(wsi) =e ^(Li)  [Equation 4],

P _(wo)=Φ_(o)(P _(wso))  [Equation 5], and

P _(wi)=Φ_(i)(P _(wsi))  [Equation 6],

wherein:

T_(o) is the temperature of air in the external area, T_(i) is thetemperature of air in the vestibule, P_(wo) is the partial pressure ofvapor in the external area, P_(w1) is the partial pressure of vapor inthe vestibule, Φ_(o) is the relative humidity of the external area,Φ_(i) is the relative humidity of the vestibule, P_(wso) is thesaturation pressure of the external area, P_(ws1) is the saturationpressure of the vestibule, L_(o) is the natural log of saturationpressure of the external area, L_(i) is the natural log of saturationpressure of the vestibule, C₈=−1.0440397×10⁴, C₉=−11.294650,C₁₀=−2.7022355×10⁻², C₁₁=1.2890360×10⁻⁵, C₁₂=−2.4780681×10⁻⁹, andC₁₃=6.5459673. Thus, the partial pressure calculation module 215 maydetermine P_(wo) and P_(wi) and provide these values to the comparatormodule 220. The comparator module 220 may receive partial pressurecalculations from the partial pressure calculation module 215, comparethe partial pressure values, and send a result to a thermal controlmodule 225.

The thermal control module 225 may receive the results of the comparatormodule 220 and, via an interface with the air moving device 116 and thetemperature conditioning device 118, may control the temperature andhumidity of air provided to the passage 108 of the vestibule 100.

FIG. 3 illustrates an embodiment of a process 300 that may be executedby the modules of the system controller 128. The process 300 may includeblocks 305 and 310, wherein the temperature of the air of the externalarea and the vestibule air are measured. These temperatures may bemeasured by the internal and external thermal sensors 122, 120,respectively. In blocks 315 and 320, the humidity of the air of theexternal area and the vestibule air may be measured, such as by theexternal and internal humidity sensors 124, 126. At blocks 325 and 330,the system controller 128 may calculate the partial pressure of moisturevapor in the external area and in the vestibule. At block 335, thesystem controller 128 may compare the partial pressures calculated inblocks 325 and 330 and determine whether the partial pressure ofmoisture vapor in the vestibule (i.e., PvV) is greater than or equal tothe partial pressure of moisture vapor in the external area (i.e., PvW).If PvV is less than PvW, the system controller 128 may execute block 340to enable a heat source. The heat source may be part of the temperatureconditioning device 118. Enabling the heat source may comprise turning aheat source in the temperature conditioning device 118 on and off. IfPvV is greater than or equal to PvW, the process 300 may restart andcontinue to monitor conditions in the vestibule and external area.

FIG. 4 depicts a block diagram of a computer system 400 suitable forimplementing the present systems and methods. Computer system 400includes a bus 405 which interconnects major subsystems of computersystem 400, such as a central processor 410, a system memory 415(typically RAM, but which may also include ROM, flash RAM, or the like),an input/output controller 420, an external audio device, such as aspeaker system 425 via an audio output interface 430, an externaldevice, such as a display screen 435 via display adapter 440, an inputdevice 445 (e.g., a keyboard, touchscreen, etc.) (interfaced with aninput controller 450), a sensor 455 (interfaced with a sensor controller460), one or more universal serial bus (USB) device 465 (interfaced witha USB controller 470), and a storage interface 480 linking to a fixeddisk 475. A network interface 485 is also included and coupled directlyto bus 405.

Bus 405 allows data communication between central processor 410 andsystem memory 415, which may include read-only memory (ROM) or flashmemory (neither shown), and random access memory (RAM) (not shown), aspreviously noted. The RAM is generally the main memory into which theoperating system and application programs are loaded. The ROM or flashmemory can contain, among other code, the Basic Input-Output system(BIOS) which controls basic hardware operation such as the interactionwith peripheral components or devices. For example, a vestibule controlmodule 200-b which may implement the present systems and methods may bestored within the system memory 415. Applications resident with computersystem 400 are generally stored on and accessed via a non-transitorycomputer readable medium, such as a hard disk drive (e.g., fixed disk475), an optical drive (e.g., an optical drive that is part of a USBdevice 465 or that connects to storage interface 480), or other storagemedium. Additionally, applications can be in the form of electronicsignals modulated in accordance with the application and datacommunication technology when accessed via network interface 485.

Storage interface 480, as with the other storage interfaces of computersystem 400, can connect to a standard computer readable medium forstorage and/or retrieval of information, such as a fixed disk drive 475.Fixed disk drive 475 may be a part of computer system 400 or may beseparate and accessed through other interface systems. A modem connectedto the network interface 485 may provide a direct connection to a remoteserver via a telephone link or to the Internet via an internet serviceprovider (ISP). Network interface 485 may provide a direct connection toa remote server via a direct network link to the Internet via a POP(point of presence). Network interface 485 may provide such connectionusing wireless techniques, including digital cellular telephoneconnection, Cellular Digital Packet Data (CDPD) connection, digitalsatellite data connection or the like.

Many other devices or subsystems (not shown) may be connected in asimilar manner (e.g., document scanners, digital cameras and so on).Conversely, all of the devices shown in FIG. 4 need not be present topractice the present systems and methods. The devices and subsystems canbe interconnected in different ways from that shown in FIG. 4. Theoperation of a computer system such as that shown in FIG. 4 is readilyknown in the art and is not discussed in detail in this application.Code to implement the present disclosure can be stored in anon-transitory computer-readable medium such as one or more of systemmemory 415, or fixed disk 475. The operating system provided on computersystem 400 may be MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, Linux®, or anotherknown operating system.

Moreover, regarding the signals and network communications describedherein, those skilled in the art will recognize that a signal can bedirectly transmitted from a first block to a second block, or a signalcan be modified (e.g., amplified, attenuated, delayed, latched,buffered, inverted, filtered, or otherwise modified) between the blocks.Although the signals of the above described embodiments arecharacterized as transmitted from one block to the next, otherembodiments of the present systems and methods may include modifiedsignals in place of such directly transmitted signals as long as theinformational and/or functional aspect of the signal is transmittedbetween blocks. To some extent, a signal input at a second block can beconceptualized as a second signal derived from a first signal outputfrom a first block due to physical limitations of the circuitry involved(e.g., there will inevitably be some attenuation and delay). Therefore,as used herein, a second signal derived from a first signal includes thefirst signal or any modifications to the first signal, whether due tocircuit limitations or due to passage through other circuit elementswhich do not change the informational and/or final functional aspect ofthe first signal.

The present description provides examples, and is not limiting of thescope, applicability, or configuration set forth in the claims. Thus, itwill be understood that changes may be made in the function andarrangement of elements discussed without departing from the spirit andscope of the disclosure, and various embodiments may omit, substitute,or add other procedures or components as appropriate. For instance, themethods described may be performed in an order different from thatdescribed, and various steps may be added, omitted, or combined. Also,features described with respect to certain embodiments may be combinedin other embodiments.

Various inventions have been described herein with reference to certainspecific embodiments and examples. However, they will be recognized bythose skilled in the art that many variations are possible withoutdeparting from the scope and spirit of the inventions disclosed herein,in that those inventions set forth in the claims below are intended tocover all variations and modifications of the inventions disclosedwithout departing from the spirit of the inventions. The terms“including” and “having” come as used in the specification and claimsshall have the same meaning as the term “comprising.”

1. An air vestibule unit configured to be positioned and provide accessbetween a first room and a second room, the first room being warmer thanthe second room, the unit comprising: an air vestibule forming a passagethrough the unit; a plurality of movable barrier members arrangedvertically to reduce external air flow through the passage; an airmoving device configured to move air into the passage; a temperatureconditioning device configured to adjust the temperature of air movedinto the passage by the air moving device; an external thermal sensorpositioned outside of the passage and configured to measure atemperature in the first room; an internal thermal sensor configured tomeasure a temperature within the passage; an external humidity sensorpositioned outside of the passage and configured to measure humidity inthe first room; an internal humidity sensor configured to measurehumidity within the passage; a system controller configured to determinea partial pressure of moisture vapor internal to the passage using thetemperature and humidity measured only in the passage and a partialpressure of moisture vapor of the first room using the temperature andhumidity measured only in the first room, and to increase thetemperature of air moved into the passage using the temperatureconditioning device if the partial pressure of moisture vapor internalto the passage is not greater less than or equal to the partial pressureof moisture vapor of the first room only.
 2. The air vestibule unit ofclaim 1, wherein the movable barrier members comprise flexible stripshanging from a top side of the air vestibule.
 3. The air vestibule unitof claim 1, wherein the movable barrier members are impact-type doors.4. The air vestibule unit of claim 1, wherein a distance through thepassage is about 6 inches or greater.
 5. The air vestibule unit of claim1, wherein the air vestibule includes lateral return air ducts havingreturn air openings at a bottom end of the air vestibule.
 6. The airvestibule unit of claim 1, wherein the system controller is configuredto maintain a partial pressure of moisture in the passage equal to orhigher than a partial pressure of moisture external to the passage. 7.The air vestibule unit of claim 1, wherein the controller is configuredto cycle the temperature conditioning device on and off.
 8. The airvestibule unit of claim 1, wherein the air moving device and temperatureconditioning device are positioned in an upper portion of the airvestibule.
 9. The air vestibule unit of claim 1, wherein the airvestibule includes side portions arranged vertically along oppositesides of the passage.
 10. A method of controlling air condition in anair vestibule unit, the method comprising: providing an air vestibuledefining a passage; positioning the air vestibule between a first roomand a second room, the first room being warmer than the second room, thevestibule providing access between the first and second rooms and beingexposed to the first and second rooms; determining an external partialpressure of moisture vapor external to the vestibule using only anexternal temperature and an external humidity in the first room;determining a vestibule partial pressure of moisture vapor within thepassage of the vestibule using a vestibule temperature and a vestibulehumidity in the passage; providing heated air to the passage with theair vestibule to increase the air temperature in the passage when thevestibule partial pressure of moisture vapor is greater than or equal tothe external partial pressure of moisture vapor.
 11. The method of claim10, wherein the vestibule temperature and vestibule humidity aremeasured using a plurality of temperature sensors and humidity sensors.12. The method of claim 11, wherein at least one of the temperaturesensors and at least one of the humidity sensors is positioned outsideof the passage.
 13. The method of claim 10, wherein the air vestibuleincludes a heat source, and the heat source is cycled on and off toprovide the heated air.
 14. The method of claim 10, further comprisingcirculating air in the vestibule by drawing air from a bottom of the airvestibule into an air moving device and expelling air from the airmoving device into the passage.
 15. The method of claim 10, furthercomprising moving heated air into the vestibule using an air movingdevice.
 16. The method of claim 15, wherein the air moved into thevestibule removes or prevents formation of at least one of ice or frostin the air vestibule.
 17. A non-transitory computer-readable mediumhaving instructions encoded thereon that, when executed by a processorof a computer, cause the computer to perform steps comprising:controlling an air vestibule, the air vestibule being positioned betweenfirst and second rooms, the first room being warmer than the secondroom, the air vestibule having a passage that provides access betweenthe first and second rooms; measuring, with a plurality of thermalsensors, an external temperature in the first room and a vestibuletemperature within the passage; measuring, with a plurality of humiditysensors, an external humidity in the first room and a vestibule humiditywithin the passage; determining an external partial pressure of moisturevapor in the first room using the external temperature and the externalhumidity only from the first room; determining a vestibule partialpressure of moisture vapor within the passage of the vestibule using thevestibule temperature and the vestibule humidity; delivering heated airto the passage if the vestibule partial pressure of moisture vapor isgreater than or equal to the external partial pressure of moisturevapor.
 18. The non-transitory computer-readable medium of claim 17,wherein the steps further comprise cycling a heat source on and off todeliver the heated air.
 19. The non-transitory computer-readable mediumof claim 17, wherein the steps further comprise circulating air in theair vestibule by drawing air from a bottom of the air vestibule andexpelling air into the passage of the air vestibule after being heated.20. The non-transitory computer-readable medium of claim 17, wherein thesteps further comprise moving air into a passage of the vestibule usingan air moving device.